Triangulation and Triangle Reduction

After you build a model, you will need to consider what it means to render the model within a game engine. The more information it takes to represent the model, the harder the game engine would need to work in order to render it. Once you build the basic model, you should go through a process called triangle reduction and triangulation.

Triangle Reduction

Triangle reduction is exactly what it sounds like...its about reducing the number of triangles needed to represent the model without overly changing the details of the object. There are several things to look out for when dealing with triangle. Before you begin working on reducing triangles, its a good idea to know what the triangle count of your model is.

Views->viewport configuration... in the statistics tab:

• check triangle count

• choose total + selection

• check Show Statistics in Active View

• hit ok

This video shows how to get this information to show in your active viewport

Choosing an appropriate amount of roundness

During the modelling process, care should be taken should be taken to choose the amount of roundness correctly... if the object is relatively small, you should reduce the roundness (number of sides on a cylinder for example) because it won't be that noticeable . If the object is larger, you will want to make it rounder

Erase all unseen triangles

Any surface that is hidden an never seen can be erased . So suppose you make a table by drawing 5 boxes (4 for the legs, 1 for the table top). The top surface on the leg is always hidden by the botton of the table top so that can be erased. If you plan for the table to always be upright (not flipped over) you can remove the bottom face of each leg also. The bottom side of the tabletop might also be removed depending on whether or not you think you will ever have a camera look at the table in a way that will show the underside of the table... might depend on height.

Study the profile of objects and erase edges

After an object is created, you could study its profile... if two segments look like a straight line, you can remove the dividing edge and its associated vertex. the object on the left has 240 triangles. The one on the right has 96.

Triangulation

When you have a quad (a face with 4 vertices. it does not need to be rectangular... just a face with 4 verts) you should take care to triangulate the vertices. This is especially true if the vertices are not coplanar (on the same plane). The quad will ultimately be divided into two triangles. This is done by connecting opposite vertices with an edge. Depending on which vertices are connected, you could end up with a shape very different than intended. Video below shows this situation:

If you have faces that have more than 4 sides, it is might be a good idea to explicitly specify the way the surface is divided into triangles:

Triangulation is also part of triangle reduction... here is an example of reducing a piece that looks very rectangular: